A program of research directed towards exploration of the utility of 3,8-dioxabicyclo(3.2.1)octane derivatives as key intermediates for stereocontrolled oxygen heterocycle synthesis is described. The rigid, conformationally well defined bicyclic heterocycles are readily prepared in a highly efficient stereoselective manner by application of the d transition metal oxo promoted oxidative cyclization of 1,5-dienes. Targets for total synthesis include the "Ortho bicyclic", a potent utero-evacuant agent containing the 3,8-dioxabicyclo(3.2.1)octane ring system, and zoapatanol, a naturally occurring utero-evacuant possessing a novel substituted oxepane ring system. Syntheses producing racemic material with relative stereocontrol, and enantiomerically enriched material will be accomplished. As a result of the novel, potentially very useful biological activity of these compounds, development of new, improved methods for their synthesis is certainly an important goal. In addition, total synthesis of the more complex oxygen heterocycles of the eunicellin class of toxic coral reef coelenterate metabolites will be explored. Specifically, total syntheses of cladiellin, an alcyonarian metabolite, and eunicellin, a gorgonian metabolite, are proposed.